How to expands multiple nested structures?

[cln-m4rie]

For Example

class ChildB(MapAttribute):
    id = UnicodeAttribute()

class ChildA(MapAttribute):
    id = UnicodeAttribute()
    child_b = ChildB()

class Parent(models.Model):
    child_a = ChildA()

Output

{
    "parent": {
        "child_a": {
            "id": "",
            "child_b": {
                "id": ""
            }
        }
    }
}